scholarly journals Lyman-alpha spectroscopy of extreme [O iii] emitting galaxies at z ≃ 2-3: implications for Lyα visibility and LyC leakage at z > 6

2021 ◽  
Vol 503 (3) ◽  
pp. 4105-4117
Author(s):  
Mengtao Tang ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot ◽  
Ryan Endsley ◽  
...  
Keyword(s):  
General Population ◽  
Ionizing Radiation ◽  
Equivalent Width ◽  
Intergalactic Medium ◽  
Line Emission ◽  
Alpha Spectroscopy ◽  
Detection Rates ◽  
Lyman Alpha ◽  
Enhanced Transmission ◽  
Extreme Line

ABSTRACT Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O iii] + H β equivalent width (EW ∼1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O iii] + H β EWs at z ≃ 2–3. At these redshifts, the IGM is highly ionized, allowing us to clearly disentangle how the Ly α properties depend on the [O iii] + H β EW. Here, we present Ly α EWs of 49 galaxies at z = 2.2–3.7 with intense [O iii] + H β line emission (EW = 300–3000 Å). Our results demonstrate that strong Ly α emission (EW >20 Å) becomes more common in galaxies with larger [O iii] + H β EW, reflecting a combination of increasingly efficient ionizing photon production and enhanced transmission of Ly α. Among the galaxies with the most extreme [O iii] + H β emission (EW ∼1500 Å), we find that strong Ly α emission is not ubiquitous, with only 50 per cent of our population showing Ly α EW >20 Å. Our data suggest that the range of Ly α strengths is related to the observed ellipticity, with those systems that appear edge-on or elongated having weaker Ly α emission. We use these results to interpret the anomalous Ly α properties seen in z > 7 galaxies with extreme [O iii] + H β emission and discuss implications for the escape of ionizing radiation from these extreme line emitting galaxies.

Census of Lyα, [OIII]5007, Hα, and [CII]158μm Line Emission with ~1000 Low-mass Lyman Alpha Emitters at z = 4.9 – 7.0 Revealed with Subaru/Hyper-Suprime Cam Survey

2018 ◽  
Vol 14 (S344) ◽  
pp. 449-452
Author(s):  
Yuichi Harikane
Keyword(s):  
Equivalent Width ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Line Emission ◽  
Flux Ratio ◽  
Lyman Alpha ◽  
Low Mass ◽  
Lyman Alpha Emitters ◽  
Turn Over

AbstractWe investigate Lyα, [Oiii] λ5007, Hα, and [Cii]158µm emission from 1,124 low-mass galaxies (typically M* ~ 108 Mʘ) at z = 4.9 - 7.0, composed of 1,092 Lyα emitters (LAEs) at z = 4.9 - 7.0 identified by Subaru/Hyper Suprime-Cam (HSC) narrowband surveys and 34 galaxies at z = 5.148 - 7.508 with deep ALMA [Cii]158µm data in the literature. At z = 4.9, we find that the rest-frame Hα equivalent width positively correlates with the rest-frame Lyα equivalent width EW0Lyα. At z = 5.7 - 7.0, there exists an interesting turn-over trend that the [ Oiii]/ Hα flux ratio increases in EW0Lyα ≃ 0 - 30 Å, and then decreases out to EW0Lyα ≃ 130 Å. We also identify an anti-correlation between a [ Cii] luminosity to star-formation rate ratio (L[CII]/SFR) and EW0Lyα at the >99% confidence level. We carefully investigate physical origins of the correlations, and find that a simple anti-correlation between EW0Lyα and metallicity explains self-consistently all of the relations identified in our study.

scholarly journals Upper limits on the escape fraction of ionizing radiation from galaxies at 2 ≲ z < 6

2021 ◽  
Author(s):  
U Meštrić ◽  
E V Ryan-Weber ◽  
J Cooke ◽  
R Bassett ◽  
L J Prichard ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Equivalent Width ◽  
Density Ratio ◽  
Groups Of Galaxies ◽  
Lyman Alpha ◽  
Alpha Emitters ◽  
Upper Limit ◽  
Lyman Continuum ◽  
Upper Limits ◽  
Lyman Alpha Emitters

Abstract In this work, we investigate upper limits on the global escape fraction of ionizing photons ($f_{\rm esc/global}^{\rm abs}$) from a sample of galaxies probed for Lyman-continuum (LyC) emission characterized as non-LyC and LyC leakers. We present a sample of 9 clean non-contaminated (by low redshift interlopers, CCD problems and internal reflections of the instrument) galaxies which do not show significant (&gt; 3σ) LyC flux between 880Å &lt;λrest &lt; 910Å. The 9 galaxy stacked spectrum reveals no significant LyC flux with an upper limit of $f_{\rm esc}^{\rm abs} \le 0.06$. In the next step of our analysis, we join all estimates of $f_{\rm esc}^{\rm abs}$ upper limits derived from different samples of 2 ≲ z &lt; 6 galaxies from the literature reported in last ∼20 years and include the sample presented in this work. We find the $f_{\rm esc}^{\rm abs}$ upper limit ≤ 0.084 for the galaxies recognized as non-LyC leakers. After including all known detections from literature $f_{\rm esc/global}^{\rm abs}$ upper limit ≤ 0.088 for all galaxies examined for LyC flux. Furthermore, $f_{\rm esc}^{\rm abs}$ upper limits for different groups of galaxies indicate that the strongest LyC emitters could be galaxies classified as Lyman alpha emitters. We also discuss the possible existence of a correlation among the observed flux density ratio $(F_{\nu }^{LyC}/F_{\nu }^{UV})_{\rm obs}$ and Lyman alpha equivalent width EW(Lyα), where we confirm the existence of moderately significant correlation among galaxies classified as non-LyC leakers.

Predicting Fetal Chromosome Anomalies in the First Trimester Using Pregnancy Associated Plasma Protein-A: A Comparison of Statistical Methods

1993 ◽  
Vol 32 (02) ◽  
pp. 175-179 ◽  
Author(s):  
B. Brambati ◽  
T. Chard ◽  
J. G. Grudzinskas ◽  
M. C. M. Macintosh
Keyword(s):  
Logistic Regression ◽  
General Population ◽  
Likelihood Ratio ◽  
False Positive ◽  
False Positive Rate ◽  
Ratio Method ◽  
Detection Rates ◽  
Gaussian Distributions ◽  
Positive Rate ◽  
Likelihood Ratio Method

Abstract:The analysis of the clinical efficiency of a biochemical parameter in the prediction of chromosome anomalies is described, using a database of 475 cases including 30 abnormalities. A comparison was made of two different approaches to the statistical analysis: the use of Gaussian frequency distributions and likelihood ratios, and logistic regression. Both methods computed that for a 5% false-positive rate approximately 60% of anomalies are detected on the basis of maternal age and serum PAPP-A. The logistic regression analysis is appropriate where the outcome variable (chromosome anomaly) is binary and the detection rates refer to the original data only. The likelihood ratio method is used to predict the outcome in the general population. The latter method depends on the data or some transformation of the data fitting a known frequency distribution (Gaussian in this case). The precision of the predicted detection rates is limited by the small sample of abnormals (30 cases). Varying the means and standard deviations (to the limits of their 95% confidence intervals) of the fitted log Gaussian distributions resulted in a detection rate varying between 42% and 79% for a 5% false-positive rate. Thus, although the likelihood ratio method is potentially the better method in determining the usefulness of a test in the general population, larger numbers of abnormal cases are required to stabilise the means and standard deviations of the fitted log Gaussian distributions.

scholarly journals Natural ionizing radiation and human health in Serbia

2010 ◽  
Vol 25 (3) ◽  
pp. 192-197 ◽  
Author(s):  
Danijela Obradovic-Arsic ◽  
Snezana Nenadovic ◽  
Dejan Filipovic ◽  
Bojana Mihajlovic
Keyword(s):  
General Population ◽  
Ionizing Radiation ◽  
Human Health ◽  
Health Effects ◽  
Population Health ◽  
Natural Radionuclides ◽  
Radiation Risk

This paper provides information about potential effects of natural ionizing radiation on general population health. Natural radionuclides are particularly stressed, as well as health effects of high and lower doses. Radio-ecological areals have been presented for Serbia, while radiation risk has been assessed for the population of Serbia according to census years.

scholarly journals What did the seahorse swallow? APEX 170 GHz observations of the chemical conditions in the Seahorse infrared dark cloud

2020 ◽  
Vol 639 ◽  
pp. A65 ◽  
Author(s):  
O. Miettinen
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Line Emission ◽  
Spectral Lines ◽  
Absorption Lines ◽  
High Mass ◽  
Mass Star ◽  
Evolutionary Trends ◽  
Detection Rates ◽  
Molecular Abundances

Context. Infrared dark clouds (IRDCs) are useful target sources for the studies of molecular cloud substructure evolution and early stages of star formation. Determining the chemical composition of IRDCs helps to constrain the initial conditions and timescales (via chemical clocks) of star formation in these often filamentary, dense interstellar clouds. Aims. We aim to determine the fractional abundances of multiple different molecular species in the filamentary IRDC G304.74+01.32, nicknamed the Seahorse IRDC, and to search for relationships between the abundances and potential evolutionary trends. Methods. We used the Atacama Pathfinder EXperiment (APEX) telescope to observe spectral lines occurring at about 170 GHz frequency towards 14 positions along the full extent of the Seahorse filament. The sample is composed of five clumps that appear dark in the mid-IR, eight clumps that are associated with mid-IR sources, and one clump that is already hosting an H II region and is, hence, likely to be in the most advanced stage of evolution of all the target sources. We also employed our previous 870 μm dust continuum imaging data of the Seahorse. Results. Six spectral line transitions were detected (≥3σ) altogether, namely, SO(NJ = 44−33), H13CN(J = 2−1), H13CO+(J = 2−1), SiO(J = 4−3), HN13C(J = 2−1), and C2H(N = 2−1). While SO, H13CO+, and HN13C were detected in every source, the detection rates for C2H and H13CN were 92.9 and 85.7%, respectively. Only one source (SMM 3) showed detectable SiO emission (7.1% detection rate). Three clumps (SMM 5, 6, and 7) showed the SO, H13CN, H13CO+, HN13C, and C2H lines in absorption. Of the detected species, C2H was found to be the most abundant one with respect to H2 (a few times 10−9 on average), while HN13C was found to be the least abundant species (a few times 10−11). We found three positive correlations among the derived molecular abundances, of which those between C2H and HN13C and HN13C and H13CO+ are the most significant (correlation coefficient r ≃ 0.9). The statistically most significant evolutionary trends we uncovered are the drops in the C2H abundance and in the [HN13C]∕[H13CN] ratio as the clump evolves from an IR dark stage to an IR bright stage and then to an H II region. Conclusions. The absorption lines detected towards SMM 6 and SMM 7 could arise from continuum radiation from an embedded young stellar object and an extragalactic object seen along the line of sight. However, the cause of absorption lines in the IR dark clump SMM 5 remains unclear. The correlations we found between the different molecular abundances can be understood as arising from the gas-phase electron (ionisation degree) and atomic carbon abundances. With the exception of H13CN and H13CO+, the fractional abundances of the detected molecules in the Seahorse are relatively low compared to those in other IRDC sources. The [C2H] evolutionary indicator we found is in agreement with previous studies, and can be explained by the conversion of C2H to other species (e.g. CO) when the clump temperature rises, especially after the ignition of a hot molecular core in the clump. The decrease of [HN13C]∕[H13CN] as the clump evolves is also likely to reflect the increase in the clump temperature, which leads to an enhanced formation of HCN and its 13C isotopologue. Both single-dish and high-resolution interferometric imaging of molecular line emission (or absorption) of the Seahorse filament are required to understand the large-scale spatial distribution of the gas and to search for possible hot, high-mass star-forming cores in the cloud.

scholarly journals Iron Line Emission from NGC1068

1989 ◽  
Vol 134 ◽  
pp. 167-172
Author(s):  
Katsuji Koyama
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Equivalent Width ◽  
Line Emission ◽  
X Rays ◽  
Iron Line ◽  
X Ray ◽  
Central Engine ◽  
Photon Index ◽  
The Continuum

X-ray emission in the 2–10 keV energy range was observed with the Ginga satellite from the Seyfert 2 galaxy NGC1068. The continuum spectrum can be described by a power-law of photon index about 1.5. An intense iron line at 6.5 keV with an equivalent width of 1.3 keV was clearly noticed. The X-ray flux was about 6 × 10 −12 erg/sec/cm2 or 3 × 1041 erg/sec, assuming a distance of 22 Mpc. The observed spectrum is consistent with the scattering and reprocessing of X-rays by the gas surrounding the central engine. With this picture we estimate that the X-ray flux of the central engine is about 1043 - 1044 erg/sec, a typical value for a Seyfert 1 galaxy.

scholarly journals Effects of Genetic Variation on Urinary Small Molecule Signatures of Mice after Exposure to Ionizing Radiation: A Study of p53 Deficiency

Metabolites ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 234
Author(s):  
Evan L. Pannkuk ◽  
Evagelia C. Laiakis ◽  
Pelagie Ake ◽  
Steven J. Strawn ◽  
Yi-Wen Wang ◽  
...  
Keyword(s):  
General Population ◽  
Ionizing Radiation ◽  
Characteristic Curve ◽  
Genotypic Variation ◽  
High Specificity ◽  
Ultra Performance Liquid Chromatography ◽  
Mitotic Catastrophe ◽  
Resistant Mouse ◽  
Hematopoietic Stem ◽  
Specificity And Sensitivity

Due to risks from potential exposures to ionizing radiation (IR), improved radiological countermeasures are required, as well as rapid high-throughput biodosimetry. Genotypic variation in the general population contributes to differences in radiosensitivity that may affect biodosimetry accuracy. Previous studies utilized radiosensitive mutant mouse models (Parp1−/− and Atm−/−) to determine the effects of genotypic deficiency on radiation signatures. Here, we extend this approach by examining changes in the urinary metabolome in a hematopoietic (HP) resistant mouse model (p53−/−) after IR exposure. As p53 is a primary regulator in radiation response and apoptosis, limited hematopoietic stem cell apoptosis leads to reduced mortality at doses of ~8–10 Gy but increased mortality at higher doses (>15 Gy) due to mitotic catastrophe in gastrointestinal (GI) crypt cells. Urine was collected from mice (wild-type (WT), p53+/−, and p53−/−) pre-irradiation and at 4 and 24 h after total body irradiation (TBI) (WT: 8 and 10 Gy; p53−/−: 10 Gy) for metabolic phenotyping using an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) platform. Minimal differences were detected between unirradiated WT, p53+/−, and p53−/− mice. While similar perturbations were observed for metabolites involved in tryptophan, vitamin B6, and histamine pathways, glycine conjugation, and redox metabolism for WT and p53−/− mice after TBI, an overall dampened response was observed in p53-deficient mice. Despite comparable metabolite patterns between genotypes, differentiation was achieved through receiver operating characteristic curve analysis with high specificity and sensitivity for carnitine, N1-acetylspermidine, and creatine. These studies highlight that both attenuated and dampened metabolic responses due to genetic variability in the general population need to be addressed in biodosimetry frameworks.

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